What are your experiences about APC solenoid mod? ( Windshield washer fluid check-valve)?
Any good influences?
Or is everybody just driving with APC box mods?
Is it same middle pipe where put the check-valve also in newer version of that APC solenoid valve?
I would like to have little bit faster spooling up in my car.
TIA!

It is the pressure supply pipe to the solenoid valve the you do the mod to.

I believe Johann F is experimenting with this mod at the moment. I have just tweaked my APC so far.

I did have some concerns about the solenoid mod causing boost spikes, but I'm waiting to hear how a careful set-up performs...

Johann F

23rd May 2002, 05:14 AM

I tried it for a short while - it goes on the line from the turbo to the solenoid. It boosted very quickly and very high before the apc cut it back to sensible levels (even with pressure cutoff disabled)I took it off as the boost was too aggressive and 'spiked' - not good for gearbox or trying to control the front wheels. I also experimented with different sizes of hole and found even a very slight reduction in the stock hole size (still much bigger than the windscreen mod) still had the same effect. I returned to tweaking the APC pots -maxed out F and gradualy reduced P until I got a nice smooth boost rise without spikes. My theory is that you can't have quick spool up without spikes - once the turbo wheel is spinning fast it's difficult to slow it down and you overshoot. Saab's APC system is designed to increase the boost in a controled way so it can maintain a steady level without the anoying surge and cutback you get with many methods of boost tweaking.
If you want boost to start earlier in the rev range - not the same thing as a decrease in spoolup time - you need a smaller turbo ie the Mitsubish TE-05 - power starts at about 700 rpm lower in the rev range than the Garrett.

Reincheck

23rd May 2002, 05:50 AM

My car takes peak boost slightly on the red and falls back after seconds to over half a way of yellow.
I looked yesterday wastegate´s actuator arm and there was no play at all, So, obviously someone has shortened that allready.
I think that I do not start to play with APC solenoid, cos you cannot get any advantage from quick spool up, if it falls very quickly right after (too much suprises in traffic). My turbo is apparently somekind of hybrid from T03, cause , I measured that the compression side turbin is between 50-55?? cannot measure that properly,cos the housing is on way, but still.

There is no much turbo lack, but the spool up could be better, now it takes too much time.
in upper revs there is plenty of (enough) power, but it feel stupid to drive, when it´s wet,it makes wheel spins on 3rd for just pedalling accelerator.

I do not have much place for options cause DI/APC , there is no easy way to get BHP´s, than just buy new eprom.
Any other ways? Idea´s?
The exhaust is allready upgraded.

I`m thinking about tweaking my APC,but I`m not sure how i should adjust the F&amp;P pots,any suggestions?I think the pressure is stock.And do I need any other mods to do this?(thinking about getting an improved downpipe and a performance exhaust system if that helps).

Your problem with the bleedoff after hitting full boost it most likely a function of your APC unit. The APC has this function in it for god knows what reason but i must agree it is annoying. The fix is simple.

There is a wire in the loom that plugs into the apc that cotrols this. Bu simple cutting it this problem (feature?) is fixed.

I am not entirely sure which wire it is but i will try chek for you.
I think others have done this also so anybody who wants to beat me to it, go ahead.

J.Ryan

25th May 2002, 11:59 AM

I thought it did that when it sensed knock to protect the engine?

john-w

25th May 2002, 01:11 PM

Have a read of this, sorta explains it all really!!
http://www.badbricks.com/main_files/faqs/apc.htm

Reincheck

27th May 2002, 03:35 PM

Hi!

Thanks John-W about the information and link.

After my engine´s total overhaul, I was afraid to give a long-time full boost for the engine, as in right way engine run-in should do. I just drove 1200 miles in 3 days(From Edinburgh,via Amsterdam,Hamburg,Fredrikshaven, Gothenburg,Stockholm to Helsinki) I am tired but car runs fine, expect lefthand broken wheel bearing.

Anyway what I noticed on that journey:

The car takes it boost just on to the redline and stays there(??) all the way end..
I tried to same thing on 3rd gear into the hill, but same result. So whatkind of baseboost do I have or do I have it all (only full boost??)

Your problem with the bleedoff after hitting full boost it most likely a function of your APC unit. The APC has this function in it for god knows what reason but i must agree it is annoying. The fix is simple.

There is a wire in the loom that plugs into the apc that cotrols this. Bu simple cutting it this problem (feature?) is fixed.

I am not entirely sure which wire it is but i will try chek for you.
I think others have done this also so anybody who wants to beat me to it, go ahead.

Which wire is it?

saab900turboguy

26th March 2009, 01:55 AM

Your engine is cutting boost back because the APC is sensing knock. Knock is when your enging is "pre detonating", or also known as the gas is igniting prematurely. In order to hold solid boost you need to add more fuel, air and also colder air. So you need a better intercooler, better injectors, 3.0bar fuel pressure regualtor and a chip. www.900aero.com (http://www.900aero.com) has a second about the apc under the DIY and TECH section. The turbo if spooling to fast will overboost thus cutting it back to base boost. Your base boost should be set between 6-7 psi which approximates at about half yellow. Be carefull not to touch the K pot or you will screw up your knock sensing and cause all kinds of problems.

nutcase

26th March 2009, 02:04 AM

Holy thread revival!!!

saab900turboguy

29th March 2009, 03:12 AM

Yea it deffinetly is, but sometimes i get bored and people are lookin for instant answers so i answer the really easy ones ;) Save them the trouble of lookin through a bunch of different threads.

ooopseyesharted

1st April 2009, 09:17 PM

Is messing with the wastegate arm a good idea on an automatic 89 900t?
I am looking for a little more low end acceleration.
The car is great otherwise(i am afraid to do the apc mod and I have an auto tranny).

saab900turboguy

2nd April 2009, 12:34 AM

all the wastegate arm does is set your base boost. This is when the apc kicks back the boost to prevent knock. Its not going to do enything to low end because the turbo needs time to spin up to make pressure. So nothing will happen until the turbo spools.

ooopseyesharted

2nd April 2009, 07:43 AM

all the wastegate arm does is set your base boost. This is when the apc kicks back the boost to prevent knock. Its not going to do enything to low end because the turbo needs time to spin up to make pressure. So nothing will happen until the turbo spools.

Ok thanks alot.

saab900turboguy

5th April 2009, 10:34 PM

To get boost without knock, you need sufficent fuel, and sufficent air. So your car has everything it needs to make combustion properly. Colder the air from the turbo to the intake the better. Hence thats why you need a good intercooler. The side mount intercooler that comes stock gets heatsoaked very quickly and does not have much air flowing to it. A front mount intercooler would be your best option alone with better injectors, 3.0bar fuel pressure regulator, intake, and a chip to manage it all. At that point you can turn up the pressure and not have much problem with boost.